1. Field of the Invention
The present invention relates to automated storage and retrieval systems (AS/RS), and more particularly to material handling systems for storing and accessing palletized material in large multi-story automated warehouse buildings.
2. Description of Related Art
Automated warehouses and automated storage and retrieval systems (AS/RS) can reduce costs, pilferage, and damage because far fewer workers are needed for otherwise similar operations.
U.S. Pat. No. 6,652,213, which is incorporated herein by reference, describes an automated storage module system. Elevators operate within exterior fixed elevator shafts amongst many floors in multi-story automated warehouse. A number of corresponding aisleways at each level of the warehouse each connect to the elevators on every level. A number of rows on each level are orthogonal to each aisleway, and allow palleted material on uniform-sized pallets to be warehoused. One aisle cart per aisleway provides a piggyback parking space on its top that can be aligned to each of the number of rows on its respective level. A row cart that is able to run along any of the number of rows on its respective level and, when aligned, it can park on the piggyback parking space on the top of any intersecting aisle cart. Such provides for independent operation by being umbilical or battery powered, and it can shuttle the palleted material along a row and aboard the intersecting aisle cart. A computer system provides for movement control of the elevators, aisle carts, and row carts with the aid of strategically placed position sensors for the carts and identity tags for the palleted material.
The row carts need to be able to lift up the pallets loaded on their backs to match the heights of shelves and elevator floors they visit. Typically, a lift of 3–5 inches is enough. Prior art lifting devices on row carts have proven to be complex, bulky, and unreliable in being able to lift straight. Combinations of lift bars and hydraulics have all been tried, often with poor results in heavy use, and even product damage. One such row cart used four jacking screws that demanded a lot of maintenance and wore rapidly.